MEE Versions
The Modular Execution Environment (MEE) supports multiple versions of its contract suite. Each version introduces new capabilities around smart accounts, validator configuration, and composability.
This guide helps SDK developers understand and select the appropriate version for their use case.
Versions Table
The table below outlines all supported MEE versions and their core capabilities. Use this to determine the best version for your project based on EVM support, composability, and ERC-7702 compatibility.
Version Breakdown
v2.3.0 (Experimental)
v2.2.2
v2.2.1 (Latest)
v2.1.0 (Default)
v2.0.0
v1.1.0
v1.0.0
Experimental and unaudited
Unlocks cross-chain orchestration for Safe accounts
- Safe accounts can now be used as master accounts in Fusion flow as well as EOAs.
- Flow is the same as for EOA’s, just instead of one master EOA signature, the proper multisig is required to initiate a SuperTxn
- Safe accounts should be deployed at the same address on all the chains involved in the SuperTxn (source and destination chains)
Recommended for projects on early stages looking to attract the large Safe multisig accounts userbase.
Audited ERC-8211 reference implementation
Nexus 1.3.2 bundling the audited ERC-8211 Smart Batching reference implementation
- Bundles the audited ERC-8211 Smart Batching reference implementation (Ethereum Foundation & Biconomy) — the formal standardization of the composability primitives shipped in earlier versions
- Expanded composability primitives and pipeline hardening
- Audited by Pashov (May 2026)
Opt-in upgrade. Will become the default once the STX API supports it natively.
Reachest features prior to v2.2.2
Built on Nexus 1.3.1 with extended composability features
- Adds native token runtime injection feature
- Adds runtime injection via custom static call (inject ANY return value as an input param at the runtime)
- Users signs EIP-712 Data Struct instead of blind Stx hash for the
smart-account mode
- Allows initializing new Nexus ERC-7702 account via relayer with an owner issued signature (gasless ERC-7702 delegation)
Recommended for projects seeking the latest features for the runtime injection and wanting to provide transparent EIP-712 sig requests for users. SDK default
Built on Nexus 1.2.0 with cutting-edge capabilities
- Fully supports ERC-7702, including delegated/upgraded EOAs as direct owners of Smart Contract Accounts (SCAs)
- Features native composability — no need for manual module installation
- Built on Nexus
1.2.0 with pre-installed MEE K1 validator
Recommended for all new projects seeking the simplest and most battle-tested developer experience.
Native Composability, No Delegated EOAs
ERC-7702 support with composability built-in
- Supports ERC-7702, but does not allow delegated or upgraded EOAs to directly own smart accounts
- Includes native composability, reducing setup complexity
Suitable for applications that do not require EOAs as direct smart account owners but want full ERC-7702 support.
EVM Paris Compatibility with Manual Composability
For chains limited to Paris upgrade opcodes
- Does not support ERC-7702
- Requires manual installation of composability modules, though the SDK automates this during deployment
Targeted for EVM chains limited to Paris upgrade opcodes (no PUSH0, MCOPY, or TSTORE). Good choice for compatibility-constrained environments.
Supports all EVM chains prior to the Cancun upgrade
Legacy compatibility for older EVM environments
- No ERC-7702 support
- Requires manual installation of composability modules, automatically handled by the SDK
- Compatible with all EVM environments below the Cancun upgrade
Suitable for legacy or specialized chains where native composability isn’t available but can be enabled via modules.
Recommendation
For most development needs, version >= 2.1.0 is strongly recommended due to its full support for delegated EOAs and native composability.
Version 2.2.1 is currently the SDK/STX default. Version 2.2.2 is available as an opt-in upgrade that bundles the audited ERC-8211 Smart Batching reference implementation, and will become the default once the STX API supports it natively.
Earlier versions remain available for legacy or specialized chains but require additional setup steps handled by the SDK.
How to Find Your Current Nexus Version
Not sure which Nexus version your smart account is using? Follow these simple steps to find out:
Locate your smart account address
Locate your existing Nexus smart account address on the specific blockchain you’re working with.
Open the block explorer
Open the block explorer for that chain (e.g., Etherscan, Polygonscan) and paste the smart account address into the search bar.
Navigate to the Contracts tab
Navigate to the Contracts tab on the explorer page.
Verify the proxy contract if needed
If the contract is a proxy and the proxy contract isn’t verified yet, you’ll need to verify it first. (If “Read as proxy” option isn’t available, this usually means verification is needed.)
Call the getImplementation function
Once verified, go to the Read as proxy section and call the getImplementation function. This will return the address of the actual implementation contract your smart account is using.
Compare with official addresses
Compare this implementation contract address against the addresses listed on our Contracts and Audits page. This will help you identify exactly which MEE version you are using. Keeping track of your Nexus version is key for smooth upgrades and compatibility checks.
Not Sure Which Version to Choose?
If you’re still confused about which MEE version fits your needs, or if you’re unsure about your current version for migration, don’t worry!
Join our Discord community to ask questions and get real-time support from the team and other developers.
We’re here to help you choose the best path forward!